Meeting Abstract
A common conception of eye evolution is the “Gradual-Morphological (GM) model”, which posits that eyes originated as a simple light sensitive patch that gradually elaborated into eyes through natural selection. Surprisingly, the prediction of GM model that simple photoreception is ancestral is rarely (if ever) tested with phylogenetic comparative methods. Furthermore, focus on the GM model draws attention away from the possibility that simple light sensors could be not precursors, but rather sometimes derived from components of complex eyes. Although data are incomplete, I will review instances of simple light sensors in modern animals whose genetic components may be descended from ancestral precursors of eyes. I will also review instances of simple light sensors in extant groups whose genetic components in contrast may be descended from more complex eyes. With additional data, these cases of ‘opsins without eyes’ could show that extraocular light sensitivity is very common in animals and may illustrate the starting point (precursor) or alternatively a derivative of the end point of the traditional GM model of eye evolution.
